1. Technical Field
This invention relates to a medical device delivery system. The medical device delivery system has a host of uses including as a stent delivery catheter system. The delivery system employs a retractable sheath which exposes a medical device for deployment.
2. General Background
Stents and delivery systems for deploying stents are highly developed and constitute a well known field of medical technology. Stents have many well known uses and applications. A stent is a prosthesis which is generally tubular and which is expanded radially in a vessel or lumen to repair dissection, prevent restenosis, or otherwise maintain its patency. Stents are widely used in body vessels, body canals, ducts or other body lumens. For the purposes of this disclosure stents and medical devices may be considered to include any stent, covered stent, stent-graft, or other generally tubular expandable prosthesis intended for placement within a lumen of a patient.
A stent may either be self-expanding or balloon expandable. For the latter type, the stent is often delivered on a balloon and the balloon is used to expand the stent. The self-expanding stents may be made of shape memory materials such as nitinol or constructed of other metals but of a design which exhibits self expansion characteristics. Stents, stent-grafts and the like are commonly delivered using a catheter delivery system. In most stent delivery systems, the stent, and the balloon if present, are held down and covered by a sheath or sleeve that extends over the stent and may extend over a substantial portion of the catheter. When the stent is suitably positioned at its desired location within the targeted vessel, the sheath or sleeve is retracted, generally in a proximal direction on the catheter, to expose the stent. When the sheath is removed, the stent is free to self-expand or be expanded with the balloon.
Throughout this specification the term proximal is used in the convention manner for that end of both the deployment device and the stent graft which is closer to the physician or other professional manipulating the device, and the term distal is used for that end of the deployment device or stent graft which in use is furthest from the physician.
A known delivery system for delivering a self-expanding stent is disclosed in U.S. Pat. No. 6,939,370. This known delivery system has a distal end adapted to be introduced into a patient and a proximal end including a handle arrangement adapted to remain outside a patient. The delivery system includes two catheters which are concentrically arranged. A nose cone dilator is positioned at the distal end of the inner catheter. The two catheters are designed to be inserted into a patient over a guide wire. The stent is carried axially around the distal end of the inner catheter. The catheter distal end has a region adapted in use to contain a stent graft. The outer catheter forms a sheath arrangement that initially extends over and covers the region containing the stent graft. The stent is carried to the delivery site while being held in a compressed delivery configuration by the outer catheter or sheath. The sheath is adapted to be moved with respect to the inner catheter by movement of the handle arrangement to expose the region containing the stent, thereby enabling deployment of the stent at the delivery site.
The handle arrangement of this known delivery system generally includes a fixed handle and a sliding handle. The sheath is fixed to the sliding handle sheath manipulator, whereby movement of the sheath manipulator with respect to the fixed handle moves the sheath independent of movement of the nose cone dilator. The sheath manipulator is located toward the distal end of the fixed handle and is adapted to slide proximally with respect to the handle to move the sheath so as to expose the region containing the stent. The distal location of the sheath manipulator is found by some physicians to be somewhat awkward to the point that such physicians occasionally move the fixed handle distally while moving the sheath manipulator proximally, thus causing the stent to expand at an untended site that is distal from the intended site. Some attempts have been made to provide a stent delivery system that provides the physician with a more easily manipulated handle mechanism that will reduce the potential for movement of the portion of the catheter carrying the stent during sheath retraction.
U.S. Pat. No. 5,733,267 discloses a pull back stent delivery system that has three concentric catheters with an inner catheter carrying a medical device such as a stent. A middle pull back catheter or sheath and an outer stiffening catheter surround the inner catheter. The inner and outer catheters are connected together at the handle end of the delivery system by a manifold stabilizer in an attempt to preclude the inner catheter from moving axially as the middle pull back catheter or sheath is retracted to provide for more accurate placement of the medical device. The manipulating handle for the middle pull back sheath is located between the ends of the manifold stabilizer. Movement of the manipulating handle for the middle pull back sheath is more controlled but a counter movement of the manifold stabilizer can still be experienced.
U.S. Pat. No. 6,709,454 discloses a stent delivery system that includes three concentric catheters with the inner and outer catheters coupled to a housing assembly which provides a manual mechanism for retracting the restraining sheath located between the inner and outer catheters. The housing assembly is designed to substantially immobilize the inner catheter, preventing it from moving relative to the restraining sheath during stent deployment. The housing assembly includes a curved base which has a contour which conforms to the patient's leg. The design of the housing tends to cause the physician to push down on the housing assembly during deployment rather than forward. This downward pressure inhibits the inner tubular member assembly from moving forward toward the patient. The design is one that allows the system to be operated by just one hand, freeing the physician's other hand for other purposes, such as stabilizing the guiding catheter during stent deployment. The sheath is coupled to a pull-back handle located in the middle of the base that is intended to be operated by the index and middle finger of the physician. The one-handed movement of this handle can still cause some undesirable forward movement of the inner tubular member.
What is still needed is a stent deployment system wherein the handle connected to the covering sheath is situated at the end of the handle nearest the physician so that movement of that handle is achieved by merely a rearward pulling movement that is not inhibited by any adjacent portion of a handle or base.